In recent years, efforts have been made to develop a method for getting a medical radiographic image without using a radiographic film made of silver halide photosensitive material. For example, there has been widespread use of Computed Radiography apparatus (hereinafter abbreviated as “CR”) that utilizes the imaging plate mainly consisting of a stimulable phosphor to pick up photostimulated luminescence using excitation light after storing the radiographic image once, and applies photoelectric conversion to this light, thereby acquiring image signals.
Further, in recent years, a proposal has been made of a Flat Panel Detector (hereinafter abbreviated as “FPD”) for reading radiographic image information by a combination of a radiographic phosphor, a radiographic conductor and a two-dimensional semiconducting detector such as a TFT switching device.
Further, to meet particular requirements of each part of the body part to be radiographed and the purpose of radiographing, a computed tomography apparatus (hereinafter abbreviated as “CT), a magnetic resonance imaging apparatus (hereinafter abbreviated as “MRI (M)”) and a mammographic apparatus (these apparatuses will be collectively called “medical image generation apparatus” hereinafter) are also employed.
These medical images are often diagnosed by the method of observing the hard copy where image information is recorded on a transmission recording medium and reflective recording medium. A medical image recording apparatus for recording medical image information on the recording medium includes the well-known method of recording an image by laser exposure on a transmission recording medium using a silver halide recording material. This method permits a monochromatic image to be rendered in excellent gradations. At the same time, it provides an advanced level of diagnostic capacity by recording it on a transmission recording medium and observing under transmitted light. Various types of medical image recording apparatuses have been developed. A thermal recording apparatus using a thermal head and heat mode laser and a photosensitive thermal color development image recording apparatus using a photosensitive thermal development recording material are also known, in addition to the method of using a silver halide recording medium requiring the prior art wet type processing.
In recent years, the aforementioned medical image generation apparatus and medical image recording apparatus are linked to a system for maintaining information in a hospital (hereinafter referred to as “HIS” (Hospital Information System)), or a system for managing information in a radiology department (hereinafter referred to as “RIS” (Radiology Information System)), via the communications network such as LAN (Local Area Network). For example, the medical image generated in various types of medical image generation apparatuses is sent to the medical image recording apparatus, where the medical image is recorded on a recording medium and is used for diagnosis.
In this case, a medical image generation apparatus selected from various types has been used in conformity to the particular site to be radiographed and the particular purpose of radiographing, whereas a medical image recording apparatus of the type conforming to the particulate site to be radiographed and the purpose of radiographing has not been used, in the prior art. To put it another way, in the prior art medical image recording apparatus, a plurality of trays are provided in one type of apparatus, and trays for accommodating the recording mediums of difference size are selected in conformity to the site to be radiographed and the purpose of radiographing. Then the medical image is recorded and outputted. Alternatively, in a medical image recording apparatus provided with a plurality of trays, a correction table storage means for storing the conversion table used for conversion of the image signal for each tray is provided, and the conversion table is corrected to suited for the photosensitive material loaded in each tray, thereby allowing image recording to be achieved at the density suited for the photosensitive material. An optical scanning recording apparatus characterized by this arrangement is also known, as disclosed in Patent Document 1, for example.
Developments are also being made to produce various types of image recording apparatuses for performing image recording using the image data obtained by a CR and FPD. The image captured by the CR and FPD is frequently required to be outputted in the same size as the affected area of a patient as a subject (life size) according to the conventional practice of simple radiographing.
In this case, when a life-sized image of the affected area is to be outputted, processing of interpolation magnification must be applied, if there is a difference between the size of the image scanned by the CR and the size of the image recorded by the image recording apparatus for creating a hardcopy and outputting it. For example, when the size of the scanned image is 87.5 microns and the size of the image recorded by the image recording apparatus is 80 microns, processing of interpolation magnification must be applied to scale up approximately 1.109 time in order to output the life-sized image.
The frequency characteristics of the image are usually deteriorated by processing of interpolation magnification based on such a non-integral multiple by spline interpolation, with the result that sharpness of the image is deteriorated. This must be avoided in a diagnostic image. If processing of interpolation magnification based on such a non-integral multiple by replication is applied, image distortion will be clearly visible. This must also be avoided in a diagnostic image.
A method is proposed to establish the relationship of an integral multiple between the size of the scanned image (reading pitch) and size of the recorded image (writing pitch), according to the thermal recording technique where the size of the recorded image at the time of hard copying is defined uniquely by the thermal head, as disclosed, for example, in Patent Document 2.
Apart from the above, a configuration is disclosed, for example, in Patent Document 3 wherein, when an image is recorded by the image recording apparatus using the image signal inputted from a plurality of image signal sources, a γ correction table corresponding to a plurality of image signal sources having different γ characteristics is stored; the γ correction table corresponding to the image signal source is set by specifying an identification number; and this image γ correction table is used to record the image signal.
Patent Document 1: Official Gazette of Japanese Patent Tokkaihei 7-250229
Patent Document 2: Official Gazette of Japanese Patent Tokkai 2000-332993
Patent Document 3: Official Gazette of Japanese Patent Tokkaihei 2-66623
In recent years, a system is composed by connecting a CR apparatus or FPD apparatus with an image recording apparatus via the network, and image data items having different reading pitches are present in a hospital equipped with this system. However, the image recording apparatus described in the Patent Document 2 is incapable of switching among multiple writing pitches and outputting the life-sized images having different reading pitches.
Further, the image recording apparatus described in Patent Document 3 provides a method for recording an image by applying γ correction corresponding to an image generating apparatus having generated this image data. However, there is no disclosure of the size of a recorded image (a writing pitch).
An object of the present invention is to provide means for recording an image through switching of multiple writing pitches and processing of interpolation to image data.